constexpr bool _Elements_are_1_byte = sizeof(_Iter_value_t<_It>) == 1;

constexpr bool _Is_sized = sized_sentinel_for<_Se, _It>;

if constexpr (_Vector_alg_in_find_is_safe<_It, _Ty>

&& (_Elements_are_1_byte ? _Is_sized || same_as<_Se, unreachable_sentinel_t>

: _Is_sized && _USE_STD_VECTOR_ALGORITHMS)

&& same_as<_Pj, identity>) {

// When _Is_sized && _Elements_are_1_byte, prefer this over memchr() for performance

_STL_INTERNAL_STATIC_ASSERT(_Elements_are_1_byte);

size_t _Count;

if constexpr (_Is_sized) {

_Count = static_cast<size_t>(_Last - _First);

_Count = SIZE_MAX;

}

// C23 7.27.5.2 "The memchr generic function"/2 says "The implementation shall behave as if

// it reads the characters sequentially and stops as soon as a matching character is found."

// C23 7.32.4.6.9 "The wmemchr generic function"/2 lacks such wording,

// so we don't use wmemchr(), avoiding issues with unreachable_sentinel_t.

_Result = static_cast<_Ptr_t>(_CSTD memchr(_First_ptr, static_cast<unsigned char>(_Val), _Count));